The only road onto Mersea Island crosses the end of the Strood and Pyefleet channels on a causeway known as the Strood. The road has been raised over the years, but below the present road can be found oak piles which indicate the presence of a causeway here in Anglo-Saxon times. The name 'Strood' is Saxon for marshy island (Strod) and the Saxons are also believed to have named the Ray nearby.
One of the oak piles from the Strood is on display in Mersea Museum and was recovered when workmen were laying electricity cables to the island. A significant number of piles were recovered when mainland water was being laid to the island in 1978 and are described in Mersea Island: the Anglo-Saxon Causeway by Philip Crummy, Jennifer Hillam and Carl Crossan, published in Essex Archaeology and History 1982. This article is summarised below:
(see http://cat.essex.ac.uk/reports/EAS-report-0023.pdf for the full report.)
Scientific dating methods have been applied to some substantial oak piles discovered beneath the Strood in 1978, when a water-main was being laid. They indicate that the structure was probably built between A.D. 684 and 702.
The piles were discovered at the south end of the causeway where the trench was at its deepest - they were about 1.6m below the present ground level and were sealed by a series of road surfaces. Seven piles were recovered and samples were submitted to Harwell laboratory for radio carbon dating to get a rough idea of the date. Samples from four of the piles were sent to the University of Sheffield for tree ring dating (dendrochronology). The remaining three piles are now in the Colchester and Essex Museum.
The dating of the construction to AD 684 to 702 was regarded as conclusive and was also a surprise as it was not known that the Strood was Saxon and no other causeway datable to 7th or 8th century is known in Britain.